This invention relates to a cementitious product reinforced by cellulosic fibres and optionally synthetic fibres.
It is well known to use asbestos fibres for the reinforcement of cementitious products. Thus, asbestos fibres find widespread use in the manufacture of asbestos cement roofing plates, such as plates sold under the trade name "Eternit".
Products made from asbestos cement present many advantageous properties, such as a high bending strength, excellent resistance against attack by chemicals and good ageing properties.
However, asbestos cement products suffer from the serious drawback that the manufacture and handling of such products present such serious health problems that is may be expected that the use of asbestos fibres as reinforcement in cementitious products will be prohibited in a few years.
It is well known to utilize a mixture of asbestos fibres and cellulosic fibres as reinforcement in the production of asbestos cement products.
However, attempts to fully replace asbestos fibres by cellulosic fibres in fibre-reinforced cementitious products and in amounts of from 0.5 to 20% by weight have failed to produce products having satisfactory strength properties. Thus, the maximum obtainable binding strength (after storage for 4 weeks) for fibre-reinforced cement products comprising pine-wood cellulosic fibres is only about 165 kp/cm.sup.2. Such bending strength is obtained by using reinforcing fibres in an amount of 4% by weight and this strength does not increase significantly when the amount of fibres is increased.
The strength mentioned above is unsatisfactory because a bending strength of at least 165 kp/cm.sup.2 is considered to be a minimum one in order to permit the replacement of asbestos cement products by products reinforced by cellulosic fibres.